Boyce–Codd Normal Form (BCNF) — Determinants as Candidate Keys If a table has been normalized so that every determinant is a candidate key, then the table is in which normal form?
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A1NF
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B2NF
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C3NF
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DBCNF
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EDK/NF (Domain-Key Normal Form)
Answer
Correct Answer: BCNF
Explanation
Introduction:BCNF refines 3NF by tightening the condition on determinants. A determinant is any attribute (or set of attributes) on which some other attribute is fully functionally dependent. This question tests recognition of the hallmark definition of BCNF.
Given Data / Assumptions:
- A candidate key uniquely identifies rows in a table.
- BCNF requires that every determinant be a candidate key.
- We assume functional dependencies are known.
Concept / Approach:3NF allows some non-key determinants if the dependent attributes are prime or meet certain conditions. BCNF removes this leniency: if an attribute set determines another, that attribute set must be a candidate key. Therefore, a table where all determinants are candidate keys is, by definition, in BCNF.
Step-by-Step Solution:1) Identify determinants in the table.2) Verify each determinant equals a candidate key.3) If true for all, the table satisfies BCNF.
Verification / Alternative check:Check sample dependencies; if any non-key attribute functionally determines another attribute, BCNF is violated, pointing to 3NF at best.
Why Other Options Are Wrong:
- 1NF/2NF/3NF: Weaker conditions; only BCNF enforces the determinant-as-key rule.
- DK/NF: Stronger still; not implied by the stated condition.
Common Pitfalls:Confusing 3NF with BCNF. Remember: BCNF tightens the determinant condition beyond 3NF.
Final Answer:BCNF